The purpose of this study is to determine how muscle takes up and burns fat present in the bloodstream. Participation is limited to persons who have maintained a constant body weight for two months prior to the study. The specific aims of this study are to determine whether: 1) Differences in resting energy expenditure, as reflected by differences in basal VO2 predict inter-individual differneces in average basal FFA flux in lean, healthy adults; 2) Gender and race (Caucasian vs African-American) influence the relationship between average VO2 and average basal FFA flux; 3) Obesty, upper body fat distribution and increased fat cell size are associated with increased fat cell size are associated with increased average basal FFA flux relative to VO2 in Caucasian and African-American adults; 4) Hepatic FFA delivery is increased in glucose intolerant (NIDDM) hypertriglyceridemic individuals (obese and non-obese) compared with glucose tolerant, nonmolipedemic individuals (obese and non-obese); 5) Intracellular muscle fatt acid fractional turnover rates and pools sizes predicted from leg arterio-venous difference techniques correlate with values obtained from muscle biopsy of the same leg; 6) Intracellular fatty acid fractional turnover rates and pools sizes in muscle are greater in obese, glucose intolerant and lean, glucose tolerant individuals. Since we began this protocol, we have developed new methods and techniques that have convinced us it is no longer justified to continue with this study. The information we would have gained from this study is being collected.